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[stingfi]

Hi all!

My 2001 Omega 2.2 with Z22XE engine is driving me nuts. The engine works normally when cold. But once it has heated up enough (roughly 40-60 degrees) the problems start. Overall it's weak, and has serious running issues especially when the gas pedal is pressed roughly 40-99 %. Here's a summary of the symptoms:

• The engine works normally when cold.
• Sluggish and weak, barely goes 140 km/h when the gas pedal is floored.
• When the gas pedal is pressed roughly 40-99 % the engine becomes very erratic. It tries to accelerate, then abruptly cuts off, then accelerates again and so on. It feels like it suddenly gives up and shuts down, only to try again in less than half a second. The whole car shakes violently. It doesn't always and continuously do this, but more often than not. And when it doesn't, it's very weak and barely accelerates unless floored.
• If I completely floor the gas pedal, the erratic behavior disappears. It's still somewhat weaker than it should be, but at least it doesn't do any abrupt cut offs and manages to accelerate in highway speeds as well.
• If I disconnect the MAF cable, the erratic behavior disappears completely. But the engine is weak and runs a bit wavy. I have tried with a brand new MAF, and the engine runs exactly like with the old one, so I think the MAF itself is OK.
• The problems have been worsening gradually with time during a couple of months.

There are no fault codes. I have checked multiple times with code reader and with the blinking light in the dashboard.

I have checked/replaced the following:

• Crank sensor replaced. It gave a fault code and had starting issues. Those were fixed with the new sensor, and all was fine until it developed the current symptoms.
• Tested with a brand new MAF and the behavior is exactly the same as with the old one. Checked MAF with code reader measuring blocks, and its signal seems fine to me.
• Replaced both lambdas. No effect. Checked with measuring blocks, and both give signal. Sensor 1 signal swings continuously up and down. To my understanding that's what it's supposed to do. Correct?

I'm out of ideas, and the car is barely driveable. Just to recap, the engine runs much better when the gas pedal is completely floored. If pressed any less than 100 % the erratic behavior starts.

So to me it seems like the ECU miscontrols the engine, maybe because the ECU itself gets incorrect signals. Could it be the cam sensor? I guess it'd give a fault code. And why would it run much better on full throttle then?

I'm very grateful for any ideas, please!

[plym ian]

Could be cam sensor or coil pack.

[stingfi]

I forgot to mention that I have also replaced the coil pack a year ago, but I replaced it with a used one. It gave a cylinder 3 misfire fault code back then and barely ran. So the pack is not new and could indeed be broken again. Last time the symptom was very different and obvious.

Can the cam sensor fail so that the ECU doesn't detect it and raise a fault code? If nothing else comes up, I'll replace it and see what happens, but I'm doubtful, because I cannot understand how it could cause these symptoms. But maybe it can.

Thanks a lot for ideas!

[tunnie]

Sensor wise, the cam sensor is about the only thing to fail on the 2.2's. 

Has been known for them to fail, but not give codes too. Genuine only for these 

[SteveAvfc.]

Had the very same problems on mine a while back changed everything that i could think of, but never changed cam sensor. Then the light bulb came on and a said cam sensor was changed. Problem solved. Worth a try and as Tunnie says genuine only  good luck:y

[stingfi]

I also feel like I've changed everything else except the cam sensor. Thank you all for comments, you've convinced me to replace that one next. Now that I've been thinking about it more, I realized that maybe the sensor can malfunction such that it does give a pulse, but too late (or maybe early). That would easily explain all the symptoms.

[stingfi]

Yesterday I replaced the cam sensor with a new one (genuine) but nothing changed.  Still works fine when cold, but when warm starts acting up. Works alright when completely floored, but with partial throttle jerks randomly (and violently). Could it really be the coil pack? Why would it work just fine when floored, but cause problems as soon as I release the pedal a little? Beats me. 

[stingfi]

I tested with a known-to-work coil pack, and absolutely no difference. Still the exact same problems. So the problem is not in the cam sensor, coil pack, crank sensor, MAF, or lambdas. While replacing the cam sensor I checked that the cam marks align, so it's not that either. I've replaced the spark plugs two years ago, but just to make sure I'll replace them again.

After that, I'm totally out of ideas. Maybe it's a broken ECU? Definitely the weirdest problem I've ever had in any car.

[Blueron]

Have you tried changing the fuel pressure regulator.I have known these to fail when car warms up.Hope you get it sorted.

[stingfi]

Thanks Blueron, that's an excellent idea. I have focused mainly on ignition related issues. But maybe it indeed is a fuel supply issue. When testing the coil pack I drove another similar Omega, and it had way more power than mine has had in a long time. I think mine has been getting more sluggish gradually over time, but I've got accustomed to it. I don't know almost anything about the Z22XE's fuel system, but it makes sense a wrong fuel pressure might cause all this.

[Andy A]

stingfi, did you find out what was causing the problem?

[johnnydog]

Having read all the symptoms, I was going to say that I would definitely put my money on the coil pack............and then I noticied that the original topic was May 2014, not this year.....!

[TheBoy]

Those symptoms smack of trims going off. Live data the trims, maf and pre cat lamda